Repowering a compressor

"charlie" wrote: (clip) the hp isn't the determining factor; it's the cfm at X psi that is required for a task.(clip) ^^^^^^^^^^^^^^^^^ Yeah, but.....Pressure x cft x some constant = HP

Reply to
Leo Lichtman
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Jon, thanks, I will look at it to see what is going on...

i
Reply to
Ignoramus7016

Maybe. I got a Quincy 2-cyl. single-stage compressor that had a 1 HP motor on it. It was quieter than the oilless unit it replaced, but still kind of noisy. But, I wanted to get the full capacity of the pump, so I put a 2 Hp motor on it, and chenged the pulley to get full motor load and rated pump RPM. To my (pleasant) surprise, the thing was actually QUIETER at the higher speed. At ~450 RPM (1 HP) the intake valves were bouncing at the ends of the stroke, and making a pronounced tone. At ~ 900 RPM (2 HP) they opened and stayed open the whole stroke, and that "tone" was only heard for a moment at shutdown. Obviously the fundamental frequency was doubled, and that would now be about 30 Hz (900/60 * 2 cylinders). It does run pretty hot, but nothing compared to an air-cooled gas engine.

Jon

Reply to
Jon Elson

Iggy I swapped out a 1800 rpm 3 hp motor on an old Champion compressor I have been using to run my shop. I had a 5 hp 3600 rpm motor that I installed with the same pulley. It has been humming along that way for eight years and daily for five years with oil changes and a belt tightening once in a while. I had to treat it to new valves last year but that was not a result of the increased speed. When I bought the valves from Phillips Air Compressors in Chicago, Fred the partsman claimed the compressor to be late 40s vintage with the RE8 pump being made till 1956. I am currently installing a 7.5 hp Speedair pump and motor on a 125 gallon tank I picked up. The tank had a 20 hp three phase motor and a big assed three cylinder compressor on it. I had to replace the tank as some fool did a scary weld patch on the 80 gal tank the Speedair came with. If any one wants either the 20 hp motor or pump contact me as I would sell both for scrap price. Mid MN is the location. I would recommend contacting the manufacturer as the pumps have quite a rpm range they can run safely at. Steve

Reply to
Up North

Jon, could reduction in noise be related to a possibility that you replaced a 3,600 RPM motor with a 1,800 RPM motor? (I am not sure if that's what happened, but if it did, maybe it contributed to noise reduction).

i
Reply to
Ignoramus7016

^^^^^^^^^^^^^^^^^^^^^^^^^^^^

All to easy to do in today's world . All they know is "buy a new one" . In response to Iggy's question , I have done pretty much what he is talking about . I'm driving an Ingersoll-Rand pump off a 20 gal tank on my

60 gal tank . The motor pulley is bigger (motor is too, hp-wise) , driving the pump at 1.5 times the original speed . Where I've seen trouble is when the designed duty cycle is exceeded . We ran a fairly large cabinet shop on two 60/6 units for a long time . Pumps were burning up because they ran so hot . I have one out in the shed that just needs new rings ... because the old ones are badly carboned up . I don't think you'll have any trouble from driving it a little faster . You might want to check the pump-up times before and after to see if the additional current draw is balanced by a shorter pump-up time .
Reply to
Snag

I think you'll find that the pump itself is a very generic unit , with many applications . See my response above .

Reply to
Snag

The compressor itself should have a max rating. You can add any motor you want but dont exceed the rating of the compressor itself.

John

Reply to
John

Best advice so far! You may be able to nearly double the RPM but at reduced compressor life, or worse, the compressor may not take the increased RPM and die a tragic death! Greg

Reply to
Greg O

It does mean that if you do run at the same speed the larger motor will last longer, and not strain under what was a full load for the smaller motor.

Reply to
Michael A. Terrell

It's a good thing I wasent drinking when I read that. :-) ...lew...

Reply to
Lew Hartswick

Bingo - Call a dealer or Curtis, and get the ratings sheet for the pump. They'll have a chart that breaks down the acceptable uses - HP input, crankshaft speed, CFM. Grainger has those charts for the Speedair pumps in their catalogs, and I expect others would have the same.

If you go off the top end of the chart, all bets are off as to how long it will hold together. When in doubt spin it at the maximum listed safe speed, and let the motor be under loaded.

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Reply to
Bruce L. Bergman

If it's a vertical tank I would be interested. Ping me off list.

JW

Reply to
jw

No, I doubled the pump RPM to double the amount of HP absorbed. The 2 Hp motor is loaded slightly above nameplate ratings at max tank pressure. And, there's no question it got "quieter" to my ears. Maybe that just shifted the tones to a less annoying frequency. But, the thing still makes a "goose honk" noise if it ever is shut down without the unloaders engaged. So, I'm quite sure that at 450 RPM it was making a specific sound that it doesn't make at 900 RPM.

I would be an idiot to replace a 1 Hp 3540 RPM motor with a 2 Hp

1725 RPM one. Or, would that be "ignoramus"? I'd be reducing my CFM by half instead of doubling it, which is what I wanted.

Jon

Reply to
Jon Elson

What I was trying to point out, but got distracted, was that just because the compressor CAME with a particular size motor doesn't mean that is the largest, or only motor that could be used. My Quincy came with a motor that was only half the HP the pump was rated for.

Jon

Reply to
Jon Elson

Motor and pump only..............no tank available. Pump might be gone today.

Reply to
Up North

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